Parsec

Parsec, unit of distance in astronomy, equivalent to 3.26 light-years. Nearby stars show a slight shift in position (a parallax) when observed from opposite sides of the earth's orbit. A star with a parallax of one second or arc (1/3,600 of a degree) is said to be one parsec away. Proxima Centauri, the nearest star, is somewhat less than 1 1/3 parsecs away.

See also: Astronomy.